2018 / Children, School, Urban

Are California Elementary School Test Scores More Strongly Associated With Urban Trees Than Poverty?

Citation

Tallis, H., Bratman, G. N., Samhouri, J. F., & Fargione, J. (2018). Are California elementary school test scores more strongly associated with urban trees than poverty? Frontiers in Psychology, 9, 2074. doi.org/10.3389/fpsyg.2018.02074

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Cities are growing faster than ever, and that growth is changing how children connect with the natural world. Beyond the emotional benefits of nature, green space around school grounds has been linked to better thinking and learning. Questions remain about these connections, including: how large is the benefit compared with other factors, and what exactly about green space makes the difference?

Researchers set out to answer both by studying 495 elementary schools across California, in communities with a wide range of incomes, backgrounds, and environments. After accounting for the usual educational influences (socio-economic status, race/ethnicity, student teacher ratio, and gender ratio) they found a clear pattern: urban schools surrounded by more trees and shrubs, within within 750 and 1000 m (1/2-2/3 mi) of the school building, had higher standardized test scores. The relationship held at those distances but not at closer ranges, and it did not appear for rural schools. Other kinds of green space, such as open fields or farmland, showed no connection to test performance at any distance.

The size of the effect matters. The strongest influence on test scores was the racial and ethnic makeup of the student body, which was associated with an 8.1% difference in scores. Tree and shrub cover around urban schools came next, linked to a 2.9 to 3.0% difference — a substantial effect once other factors were taken into account. Urban schools with average tree cover scored about 4.2% higher on standardized tests than urban schools with very little tree cover.

These results point to something practical: the trees and shrubs in a neighborhood, not just on the school grounds themselves, appear to support students’ learning. That makes neighborhood-scale greenery a factor worth taking seriously in conversations about school environments, and a strong reason to test tree-planting programs directly, to see whether adding trees can measurably improve educational outcomes.

Abstract

Figure 1. Model selection results for several common variables for student test performance on a sample of California fifth grade classes. Effect sizes (A) were significant for urban/rural location, % minority representation and % student body on free and reduced lunches. Minority representation (B) showed the strongest signal, with a two SD difference in minorities associated with a 100 point difference in overall test scores.

Unprecedented rates of urbanization are changing our understanding of the ways in which children build connections to the natural world, including the importance of educational settings in affecting this relationship. In addition to influencing human-nature connection, greenspace around school grounds has been associated with benefits to students’ cognitive function. Questions remain regarding the size of this benefit relative to other factors, and which features of greenspace are responsible for these effects. We conducted a large-scale correlative study subsampling elementary schools (n = 495) in ecologically, socially and economically diverse California. After controlling for common educational determinants (e.g., socio-economic status, race/ethnicity, student teacher ratio, and gender ratio) we found a significant, positive association between test scores and tree and shrub cover within 750 and 1000 m of urban schools. Tree and shrub cover was not associated with test scores in rural schools or five buffers closer to urban schools (10, 50, 100, 300, and 500 m). Two other greenspace variables (NDVI and agricultural area) were not associated with test performance at any of the analyzed buffer distances for rural or urban schools. Minority representation had the largest effect size on standardized test scores (8.1% difference in scores with 2SD difference in variable), followed by tree and shrub cover around urban schools, which had a large effect size (2.9–3.0% at 750 and 1000 m) with variance from minority representation and socioeconomic status (effect size 2.4%) included. Within our urban sample, average tree-cover schools performed 4.2% (3.9–4.4, and 95% CI) better in terms of standardized test scores than low tree-cover urban schools. Our findings support the conclusion that neighborhood-scale (750–1000 m) urban tree and shrub cover is associated with school performance, and indicate that this element of greenspace may be an important factor to consider when studying the cognitive impacts of the learning environment. These results support the design of experimental tests of tree planting interventions for educational benefits.